Transcript ParkedOnHill.pptx

Parking on a Hill:
Friction
Our Friction Lab
• A 10 pound block (A) is pulled by a
5 pound block (B) which is hanging
from a pulley.
• Normal force = FN = 10 pounds
• Tangential force = FT = 5 pounds
• Maximum force of friction
= µ ∙ FN = .6 ∙ 10 = 6 pounds
• Forces on A
–
–
–
–
Gravity Down: 10 pounds
Table Up:
10 pounds
String Right:
5 pounds
Friction Left:
5 pounds
Components
A 1000 Pound Car on a Hill in Manayunk
Normal Force – Perpendicular to the road
Tangential Force – Parallel to the road
If the coefficient of friction is .4, will the car slip?
Suppose the hill is inclined with an angle of 20°
with the horizontal. ( µ=.4)
• Geometry
• Trig
sin 20 = opp/hyp
= FT/1000
cos 20 = adj/hyp
= FN/1000
• Algebra
FT =1000 ∙ sin 20 = 342 pounds
FN =1000 ∙ cos 20 = 940 pounds
• Physics
Maximum Friction = µs∙FN =
Car does not slide
.4 x 940 = 376 pounds